1. Field of the Invention
This invention relates to a thermal printer, and, more particularly, to a control system for maintaining a surface temperature of the thermal head at a predetermined level.
2. Description of the Prior Art
In the case of printing letters and characters by a printer using a thermal head, if it is done by electric conduction for a certain definite time period through each dot of the thermal head, the surface temperature of the head at the time of printing tends to vary depending on the temperature of the same before the printing. For instance, the surface temperature of the thermal head, when effecting electric conduction thereto for a certain definite time period, differs between the following two situations: where the temperature of the head has lowered to an ambient temperature due to its having not been used for a certain period of time and where the surface temperature of the head has already risen to a certain level owing to its continuous use by that time. As the consequence of this, there occurs irregularity in the heat quantity to be imparted to heat-sensitive paper and image transfer tape, which makes it difficult to obtain the print of a uniform density, hence inferior print quality.